Tom Jenkins
Lifetime Supporting Member
.... I need to keep the flow leaving the product tank as constant as I can, using the 12m height (workable range 9m) as a buffer which is allowing the product to rise and fall without affecting the flow as best as is possible......
..... I do not know the rate at which the product is entering the tank .....
This is not a training problem. This is not a tuning problem. This is not a problem that can be solved with differential equations. This is an example of the laws of nature overriding the desires of an engineer.
A simple feedback control loop, PI or PID or whatever, should be able control the flow out by modulating pump speed. At that point, given your control system measurements, you are done.
Assume for sake of argument that control out of the tank is working perfectly and you have a constant flow out of the tank. If the flow into the tank is greater than the flow out of the tank then the tank level will rise. There is nothing you can do about that. The rate of level increase will be a direct function of the difference in the two flows and the area of the tank.
If the flow into the tank is lower than the flow out the level will fall according to the same relationship.